1. Field of the Invention
The present invention relates generally to electronic devices that are sensitive to light or other forms of radiation. More particularly, the present invention relates to packages with transparent coverings for enclosing image sensors and methods for their assembly.
2. State of the Art
Solid-state image sensors, for example, charge coupled devices (CCDs) or complementary metal-oxide semiconductor (CMOS) chips, are increasingly in demand for use with electronic devices such as digital cameras. Conventionally, these sensors have been packaged for use by mounting them to a substrate and enclosing them within a housing assembly. The housing assembly incorporates a transparent lid to allow light or other forms of radiation to be received by the sensor. The lid may be a flat window or shaped as a lens to provide optical properties. The substrate and housing are often formed from a ceramic material, and the lid is glass or a similar transparent substance attached to the housing by an adhesive. Due to the materials and structure involved, this packaging technique may be expensive and difficult to manufacture. Further, growing desire for portable electronic devices that will stand up to extreme environments raises concerns of durability and size.
In order to better meet large-scale production requirements, various methods have been developed in attempts to simplify the construction of image sensors. Examples include U.S. Pat. No. 6,266,197 to Glenn et al., which discloses fabricating multiple sensor housings at one time by molding window arrays. U.S. Pat. No. 6,072,232 to Li et al. discloses a plastic package with an embedded frame for reducing material costs. U.S. Pat. No. 5,811,799 to Wu discloses a simplified substrate that is a printed wiring frame with a wall erected thereon. While these and other designs have been of some benefit, they still involve a number of specialized parts requiring multiple, sometimes precision, steps for assembly. Issues concerning material costs and part complexity remain.
Accordingly, a need exists for improved image sensor packaging that is simple to assemble and cost effective, while being of durable and light construction.